System and method for transporting SS7 signaling over broadband asynchronous transfer mode links

ABSTRACT

A high speed signaling network includes a high speed transport virtual circuit network, and a plurality of advanced intelligent network nodes coupled to the high speed transport virtual circuit network via a plurality of high speed links transporting signaling data.

TECHNICAL FIELD OF THE INVENTION

This invention is related in general to the field of telecommunicationssystems. More particularly, the invention is related to a system andmethod for transporting SS7 signaling over broadband asynchronoustransfer mode links.

BACKGROUND OF THE INVENTION

As telecommunication networks approach the next century, the everincreasing demand for new services and applications require a rapidexpansion of the intelligent signaling and switching networks. In theintelligent network (IN) or advanced intelligent network (AIN),Signaling System Number 7 (SS7) is the signaling protocol for thetelecommunications network which is transmitted over 56 or 64 Kbps datalinks. The SS7 links interconnect signal transfer points (STP), serviceswitching points (SSP), and service control points (SCP) in the typicalintelligent network architecture.

The increasing traffic volume of the telecommunications network coupledwith new intelligent service offerings result in a bulky SS7 networkwhich may become a troublesome bottleneck that can negatively impact thenetwork's ability to route calls and provide services. New services,such as local number portability, require a per-call query and responsewith a network database. These new services are likely to drive currentdata links to full capacity and introduce additional call set-up delaysusing the lower speed data links used in today's network. The need fordecreasing signaling latency will be of critical importance as end usersperceive the quality of service from their chosen carrier.

The signal transfer point performs the message transfer protocol (MTP)routing, management functions for the SS7 user layers and the SCCP(signaling connection control part) functions. The signal transferpoints are typically arranged in pairs to provide signaling redundancyfor service switching points and for service control points in a typicalSS7 network architecture. The SS7 network is integral to call controlfunctions.

SUMMARY OF THE INVENTION

Accordingly, a need has arisen for a solution to the congestion problemthat may arise with the SS7 networks. The teachings of the presentinvention provides a system and method for transporting SS7 overbroadband asynchronous transfer mode links.

In one aspect of the invention, a high speed signaling network includesa high speed transport virtual circuit network, and a plurality ofadvanced intelligent network nodes are coupled to the high speedtransport virtual circuit network via a plurality of high speed linkstransporting signaling data.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, reference may bemade to the accompanying drawings, in which:

FIG. 1 is a simplified block diagram of an exemplary advancedintelligent network;

FIG. 2 is diagram of the broadband SS7 layered architecture with theasynchronous transfer mode layer;

FIG. 3 is a simplified block diagram of major broadband SS7 functionalprocesses in the broadband SS7 platform;

FIG. 4 is a simplified functional block diagram of the broadband SS7platform;

FIG. 5 is a simplified block diagram of an embodiment of a signalingconnection control part process of the SS7 user parts;

FIG. 6 is a simplified block diagram of an embodiment of an ISDN userpart process of the SS7 user parts;

FIG. 7 is a simplified block diagram of an embodiment of a broadbandISDN user part process of the SS7 user parts;

FIG. 8 is a simplified block diagram of an embodiment of a messagetransfer part process; and

FIG. 9 is a simplified block diagram of an embodiment of a high speedsignaling network.

DETAILED DESCRIPTION OF THE INVENTION

The preferred embodiments of the present invention are illustrated inFIGS. 1-9, like reference numerals being used to refer to like andcorresponding parts of the various drawings.

FIG. 1 shows an exemplary telecommunications network 10 such as anadvanced intelligent network (AIN) or intelligent network (IN). Network10 includes a service control point (SCP) 14 and a mated pair of signaltransfer points (STPs) 16, which are coupled to one another with SS7 `B`type signaling links. Service control point 14 is directly linked tosignal transfer point 106 via an SS7 (signaling system number 7) `A`type signaling link set 18. An SS7 link set may include up to sixteensignaling data links. Signal transfer points 16 are further coupled toone or more service switching points (SSPs) 22 and 24, via SS7 link sets20 consisting of `A` links. Service switching points perform theswitching and call handling functions in the network.

Service control point 14 is a transaction based processing system whoseprimary responsibility is to respond to queries from service switchingpoints 22 for data needed to complete routing a call. Service switchingpoints 22 are part of the public switched telephone network and arecoupled to the customer premises equipment (CPE) 28 of telephone servicesubscribers. Signal transfer points 16 may be coupled to at least oneother mated pair signal transfer points 30 via an SS7 link set 32comprising `D` type signaling links. Signal transfer points 30 is alsocoupled to a service control point 33 via `A` type links and to serviceswitching points 34 via SS7 `A` type link sets 36. A plurality ofcustomer premises equipment 38 are coupled to service switching points34.

It may be seen that certain SS7 link sets may become points ofcongestion in the SS7 network 46. For example, SS7 link set 18 betweenservice control point 14 and signal transfer point 16 may be abottleneck for transporting database queries originating from multiplecentral offices. As such, the capacity of SS7 link set 18 may severelyrestrict the service control point's ability to service large volumes ofcalls. With the offering of new services, often multiple databasequeries transmitted on links in SS7 network 46 are required to completea call. For example, service control point 14 provides a centralizeddatabase for many services, which includes a local number portability(LNP) database, a line information database (LIDB), and a calling name(CNAM) database; and signal transfer point 16 may include global titletranslation (GTT) databases such as an LNP GTT, an LIDB GTT, switchbased services GTT, CNAM GTT, local number portability databases andinterswitch voice messaging (ISVM) GTT databases containing routing datarelated to each service.

Similarly, SS7 signaling link set 32 coupling mated pair signal transferpoints 16 and 30 may become congested as queries between service controlpoints 14 and 33 are consumed by queries between regions or acrossnetwork boundaries.

FIG. 2 is a block diagram showing a combined narrowband and broadbandSS7 architecture 60 which provides SS7 interworking functions betweennarrowband SS7 and broadband SS7. As in the SS7 protocol, broadband SS7architecture also includes two parts, a message transfer part (MTP) 62and user parts 64. Message transfer part 62 contains the necessarymechanism to ensure reliable transmission of functional signalingmessages with maximum network availability. User parts 64 providecriteria for application and service management. User parts 64 mayinclude ISDN (integrated services digital network) user part (ISUP) 70,narrowband and broadband SCCP 72, TCAP (transaction capabilitiesapplication part) (narrowband and broadband) 74, and broadband ISDN userpart 76. One of the primary characteristics of broadband SS7 messages isthe longer message size--4096 bytes versus 274 bytes. SCCP 72 and TCAP74 each contain broadband extensions for compatibility with thebroadband message size. B-ISUP 76 differs from ISUP 70 by supportingspecific messages and parameters for broadband services as specified byITU industry standards (Q.2764). Message transfer part 62 of SS7includes three levels: message transfer part layer 1 80, messagetransfer part layer 2 82, and message transfer part layer 3 84.Similarly, message transfer part layer 3 also contains broadbandextensions to support broadband services. In broadband SS7 architecture60, provisions are made for transmitting SS7 signaling over broadbandlinks (OC-3 or STM-1) operating at 155 Mbits/second. This is achieved byreplacing SS7 message transfer part layers 2 and 1 with SAAL (signalingATM adaptation layer) 90, which includes asynchronous transfer mode(ATM) SSCF (service specific coordination function) 92, SSCOP (servicespecific connection oriented protocol) 94, and ATM adaptation layer 96(AAL) functionalities. SSCOP is a connection oriented protocol witherror recovery providing a generic data transfer service for differentATM adaptation layer services defined by the SSCF. The primary functionof the SSCF is to map the services of the SSCOP to the requirements ofMTP layer 3. Message transfer part layer 1 80 is replaced by anasynchronous transfer mode layer 98 and an asynchronous transfer modephysical medium dependent layer 100. Message transfer part layer 1 80includes an interface to V.35/RS-449 narrowband link, and asynchronoustransfer mode physical layer 100 includes an interface to a broadbandOC-3 or STM-1 link.

Referring to FIG. 3, the major functional processes of broadband SS7protocol implementation include an SS7 platform manager 120, an SS7 userparts process 122, a message transfer part layer 3 process 124, and adata link and physical layer process 126. SS7 user parts 122 accessesmessage transfer part layer 3 124 via a service access point (SAP) 128.SS7 platform manager 120, also shown in FIG. 4, is responsible for theconfiguration and monitoring of a broadband SS7 platform 130 as well asinter-process communications. SS7 platform manager 120 configures thesystem from configuration files 132, which are read upon start-up ofbroadband SS7 platform 130. Configuration files 132 may be modifiedwithout interrupting SS7 traffic. A user interface 134 may also beprovided to SS7 platform manager 120 for interactive access to broadbandSS7 platform 130. User interface 134 provides access to the control,statistics and status interfaces for SS7 user parts processes 122,message transfer part layer 3 process 124, and the broadband signalinglink components. The SS7 platform manager 120 provides layer managementto all the components within the architecture via a layer managementmessaging protocol.

SS7 user parts process 122 implements the services and applicationswhich broadband SS7 platform 130 supports, which may include ISDN userpart, SCCP, TCAP, and broadband ISDN user part. ISDN user part andB-ISDN user part require a service access point layer on asession-by-session basis (see FIGS. 6 and 7) SCCP process 140 providesadditional functions to the message transfer part layer 3 124 to supportconnection-less and connection-oriented network services. SCCP process140 also supports a logical addressing capability among database andintelligent network applications using SS7 network 46 (FIG. 1). SCCPprocess 140 acts as a network service provider and provides networksubsystem routing for user layers 154, including TCAP 150. SS7 platformmanager 120 has configuration and management access to SCCP process 140layer.

The SS7 user parts process also includes a TCAP process 150 depicted inFIG. 5, which provides a way for intelligent applications to communicateacross SS7 network 46 from one application processing platform to adestination application. TCAP process 150 which interfaces with SCCPprocess 140, may include a programmable application program interface(API) library 152 to enable user applications 154 access to TCAPservices.

SS7 user parts 122 may also include an ISDN user part process 160, shownin FIG. 6. The ISDN user part is a protocol for circuit related messagesand is used to set up and tear down all circuits used for data or voicecalls in the public switched telephone network. ISDN user part process160 may interact directly with the message transfer part process 124instead of using the services of the SCCP. User of SCCP for ISDN userpart 160 is for further study.

Referring to FIG. 7, a broadband ISDN user part (B-ISUP) process 166supports broadband ISDN user part through SS7 network 46. Broadband ISDNuser part process 166 interfaces with message transfer part process 124with message transfer part service primitives instead of using theservices of SCCP.

Referring to FIG. 8, message transfer part layer 3 process 124implements the message routing, message distribution and messagediscrimination part of the broadband SS7 platform. Message processingbegins in message transfer part layer 3 124. Message transfer part layer3 124 relies on the services of data link and physical layer 126 fordelivery of all messages. The interface between the two layers consistsof a set of primitives. Message transfer part layer 3 124 also usesprimitives to communicate with SS7 user parts 122, i.e., SCCP 140, ISUP162, and B-ISUP 166. A service access point 128 is established for eachsession between B-ISUP 166 and message transfer part layer 3 124 andalso between ISUP 160 and message transfer part layer 3 124 (shown inFIGS. 6 and 7). A message transfer part layer 3 API library 170 may beprovided for applications who wish to directly access the messagetransfer part service primitives.

Data link and physical layer process 126 provides the message transferpart layer 3 process 124 with either a narrowband or broadband signalinglink. The narrowband signaling link configuration is provided throughSS7 message transfer part layers 1 and 2. The broadband signaling linkconfiguration may be provided through SAAL which provides SSCOP and SSCFfunctionality. Data link and physical layer 126 delivers the messagetransfer part layer 3 messages. In a narrowband SS7 implementation,message transfer part layer 3 interfaces with a message transfer partlayer 2 82 (FIG. 2). To support the SS7 signaling over an asynchronoustransfer mode link the message transfer part layer 3 interfaces with aSAAL (signaling asynchronous transfer mode adaptation layer) 90.However, message transfer part layer 3 accesses the asynchronoustransfer mode layer 2 functionality with the same set of primitives asthose used to interface with message transfer part layer 2. Data linkand physical layer 126 may have three possible configurations inbroadband SS7 platform depending on whether it supports narrowband,broadband signaling links, or both. Broadband SS7 platform 130 providesnarrowband signaling links by integrating message transfer part layer 3with an message transfer part layer 2 and 1 and ultimately a physicallink supporting V.35, RS-449 or DSOA (data service operations andadministration interface protocol) physical interfaces. Broadbandsignaling links may be provided by integrating the message transfer partlayer 3 with SAAL 90 to the OC-3 link. SAAL 90 functionality is providedby SSCF and SSCOP.

SS7 message signaling units (MSUs) are assembled into standardasynchronous transfer mode packets which includes physical data units(PDUs). The transmission facility includes virtual channels that providean end-to-end virtual path which may be a permanent virtual circuit(PVC) and/or a switched virtual circuit (SVC). However, thecharacteristics of SS7 ISUP and SS7 TCAP traffic suggest that when adata link is established, aligned and becomes operational, it generallyremains in this state for an extended period of time. Therefore, it ismore likely that permanent virtual circuits will be used in network 215rather than switched virtual circuits though it is a matter of operatorchoice. The virtual path connection is defined based on theinterpretation of the higher layer SS7 message transfer protocol (MTP-3)that includes a destination point code which identifies the physicallocation of the termination point of the signaling path. Within thevirtual path the facility is allocated into multiple virtual channels.The signaling bandwidth of the virtual channel is limited only by thesize of the medium or total bandwidth of the physical facilityestablished by industry standards. In this scheme, the broadbandasynchronous transfer mode transport does not use point-to-pointphysical connections, but virtual circuits, whether they may be switchedor permanent. This is different from network topologies contemplated byother entities, such as Bellcore. Bellcore has promulgated the GenericRequirements for CCS Nodes Supporting ATM High-Speed Signaling Links(HSLS), GR-2878-CORE, November 1995, which is incorporated herein byreference.

Service control point 204 may be coupled to network 215 by an electricalfacility (DS-1 or E1) or an optical facility (OC-3 or STM-1) link set216 using asynchronous transfer mode signaling to transport SS7. Signaltransfer points 202 are coupled to network 215 by optical link sets 216which may transport asynchronous transfer mode OC-3 or STM-1 formatsignals. Signal transfer point 203 may also provide physicalconnectivity for electrical DS-0 (single channel) based SS7 signalingdata links 207 and electrical channelized and fractional T1/E1/T3/E3 SS7signaling data links over a singular transmission facility 209 to legacynetwork nodes 213, as well as optical SS7 signaling OC-3/STM-1 datalinks 216 to asynchronous transfer mode network 215. In this manner,signal transfer point 203 supports signaling for both circuit-based andpacket-based connectivities. As specified by industry standards, thelink sets in the asynchronous transfer mode SS7 network may have up to16 links, and load balancing between the 16 links in a link set may beperformed with known techniques in the art. Further, any link within alink set may be dynamically loaded with the total capacity of thefacility bandwidth to any level of occupancy of the virtual channel solong as the total facility bandwidth has not been exceeded by the totalusage of all available channels.

Although the present invention and its advantages have been described indetail, it should be understood that various mutations, changes,substitutions and alterations can be made therein without departing fromthe spirit and scope of the invention as defined by the appended claims.

What is claimed is:
 1. A high speed signaling network, comprising:a highspeed transport virtual circuit network; and a plurality of advancedintelligent network nodes coupled to the high speed transport virtualcircuit network via a plurality of high speed links transportingsignaling data and bearer data, each of the plurality of advancedintelligent network nodes operable to interwork between narrowband andbroadband signaling protocols.
 2. The high speed signaling network, asset forth in claim 1, wherein the high speed transport virtual circuitnetwork comprises permanent virtual circuits.
 3. The high speedsignaling network, as set forth in claim 1, wherein the high speedtransport virtual circuit network comprises switched virtual circuits.4. The high speed signaling network, as set forth in claim 1, whereinthe plurality of high speed links coupling the advanced intelligentnetwork nodes to the high speed transport virtual circuit networkcomprises at least one link and no more than 16 links within a singlelink set.
 5. The high speed signaling network, as set forth in claim 1,wherein the plurality of high speed links comprise asynchronous transfermode multi-channel transmission facilities.
 6. The high speed signalingnetwork, as set forth in claim 1, wherein the plurality of advancedintelligent network nodes comprise a service control point.
 7. The highspeed signaling network, as set forth in claim 1, wherein the pluralityof advanced intelligent network nodes comprises a signal transfer point.8. A high speed signaling network, comprising:a high speed transportvirtual circuit network; and a plurality of advanced intelligent networknodes coupled to the high speed transport virtual circuit network via aplurality of high speed links transporting signaling data and bearerdata, wherein the plurality of high speed links comprise asynchronoustransfer mode transmission facilities carrying SS7 signaling data links.9. The high speed signaling network, as set forth in claim 8, whereinthe plurality of high speed links comprise electrical-based asynchronoustransfer mode transmission facilities carrying SS7 signaling data links.10. A method for transporting signaling data over high speed data links,comprising the steps of:coupling network nodes to a high speed virtualcircuit network with high speed SS7 data link sets; coupling eachnetwork node to the high speed virtual circuit network with a redundanthigh speed SS7 data link set; load balancing among the data links withineach high speed SS7 data link set; and interworking between narrowbandsignaling and broadband signaling.
 11. The method, as set forth in claim10, further comprising the step of converting DS-0 circuit-based SS7signaling data to packet-based asynchronous transfer mode signalingdata.
 12. The method, as set forth in claim 10, further comprising thestep of converting electrical circuit-based SS7 signaling data tooptical packet-based asynchronous transfer mode signaling data.
 13. Themethod, as set forth in claim 10, further comprising the step ofconverting electrical circuit-based SS7 signaling data to electricalpacket-based asynchronous transfer mode signaling data.
 14. A method fortransporting signaling data over high speed data links, comprising thesteps of:coupling network nodes to a high speed virtual circuit networkwith high speed SS7 data link sets; coupling each network node to thehigh speed virtual circuit network with a redundant high speed SS7 datalink set; load balancing among the data links within each high speed SS7data link set; and converting circuit-based SS7 signaling data intopacket-based asynchronous transfer mode packets.
 15. The method, as setforth in claim 14, wherein the circuit based SS7 signaling data is inDS-0 signals.
 16. The method, as set forth in claim 14, wherein thecircuit based SS7 signaling data is in electrical signals and the packetbased asynchronous transfer mode packet data are in optical signals. 17.The method, as set forth in claim 14, wherein the circuit based SS7signaling data is in electrical signals and the packet basedasynchronous transfer mode packets are in electrical signals.